Grupo CIBIOP, Departamento de Ingeniería de Procesos, Universidad EAFIT, Carrera 49 No. 7 Sur 50, Medellín, Colombia.
Departamento de Bioquímica y Biología Molecular-A, Facultad de Veterinaria, Universidad de Murcia, Campus de Espinardo, E-30100 Murcia, Spain.
Colloids Surf B Biointerfaces. 2017 Aug 1;156:114-122. doi: 10.1016/j.colsurfb.2017.05.021. Epub 2017 May 10.
Lipopeptide biosurfactants constitute one of the most promising groups of compounds for the treatment and prevention of fungal diseases in plants. Bacillus subtilis strain EA-CB0015 produces iturin A, fengycin C and surfactin and it has been proven useful for the treatment of black Sigatoka disease in banana plants, an important pathology caused by the fungus Mycosphaerella fijiensis (Morelet). We have found that B. subtilis EA-CB0015 cell free supernatants and purified fractions inhibit M. fijiensis cellular growth. The effect of the purified lipopeptides mentioned above on fungal growth has been also evaluated, observing that iturin A and fengycin C inhibit mycelial growth and ascospore germination, whereas surfactin is not effective. On the hypothesis that the antifungal action of the lipopeptides is associated to their incorporation into biological membranes, ultimately leading to membrane permeabilization, a detailed biophysical study on the interaction of a new isoform of fengycin C with model dipalmitoyphosphatidylcholine (DPPC) membranes has been carried out. Differential scanning calorimetry shows that fengycin C alters the thermotropic phase transitions of DPPC, and is laterally segregated in the fluid bilayer forming domains. Fluorescent probe polarization measurements show that fengycin C does not affect the hydrophobic interior of the membrane. This latter perturbation is concomitant with a strong dehydration of the polar region of DPPC, as shown by FTIR. Fengycin-rich domains, where the surrounding DPPC molecules are highly dehydrated, may well constitute sites of membrane permeabilization leading to a leaky target membrane. These results are a solid support to explain the membrane perturbing action of fengycin, which has been related to its antifungal activity.
脂肽生物表面活性剂是治疗和预防植物真菌病最有前途的化合物之一。枯草芽孢杆菌 EA-CB0015 产生伊枯草菌素 A、芬净 C 和表面活性素，已被证明对香蕉黑星病的治疗有用，黑星病是由真菌木贼镰孢（Morelet）引起的重要病理学。我们发现，枯草芽孢杆菌 EA-CB0015 的无细胞上清液和纯化级分抑制了 M. fijiensis 的细胞生长。还评估了上述纯化脂肽对真菌生长的影响，观察到伊枯草菌素 A 和芬净 C 抑制菌丝生长和分生孢子萌发，而表面活性素则无效。基于脂肽的抗真菌作用与其掺入生物膜相关的假设，最终导致膜通透性增加，我们对新型芬净 C 同型与模型二棕榈酰磷脂酰胆碱（DPPC）膜的相互作用进行了详细的生物物理研究。差示扫描量热法显示，芬净 C 改变了 DPPC 的热致相转变，并在形成域的流体双层中横向分离。荧光探针偏振测量显示，芬净 C 不影响膜的疏水区。这种后期的扰动伴随着 DPPC 极性区域的强烈去水合作用，如 FTIR 所示。富含芬净 C 的区域，周围的 DPPC 分子高度去水合，可能是导致膜通透性增加导致靶膜渗漏的部位。这些结果为解释芬净 C 的膜扰动作用提供了有力支持，该作用与它的抗真菌活性有关。
